The present invention relates to a dual drive driveline for vehicles. The invention further relates to a vehicle comprising said driveline, in particular to an off-highway vehicle such as an agricultural vehicle or a wheel loader.
Dual drive hydrostatic transmission drivelines known from the prior art typically include a power source in driving engagement with a hydrostatic pump and two hydrostatic motors in fluid communication with the hydrostatic pump. Generally, the output torque of the first hydrostatic motor and the output torque of the second hydrostatic motor are summed in a summing gearbox. From an output shaft of the summing gearbox the summed torque is transmitted to at least one vehicle axle or wheel shaft. Typically, the torque transmission from the output shaft of the summing gearbox to the axle is realized using at least one driveshaft and at least one bevel set.
In order to improve the overall transmission efficiency of the driveline and in order to reduce energy consumption, the summing gearbox is often configured such that the ratio of motor output torque to the output torque of the summing gearbox differs for the two motors. For example, said ratio is smaller for the first motor than for the second motor. In this case, the driveline is usually configured such that the first motor can be disengaged at higher vehicle speeds in order to avoid overspeeding of the first motor. Thus, at low vehicle speed both motors are used to provide the maximum output torque while at high vehicle speed, for example above a threshold vehicle speed, only the second motor is engaged. In this way, energy consumption and overall losses can be reduced.
However, despite these improvements a need for even more efficient drivelines continues to exist. In the off-highway market in particular there is a growing demand for drivelines that allow the transmission to be adapted to different driving conditions such as vehicle speed or ground conditions.